Gas turbine engines include a plurality of rotors, including one or more compressor rotors. The rotors typically comprise a circumferential array of blades extending from a hub. The blades have an airfoil shaped portion, characterised by a pressure side, a suction side, a leading edge and a trailing edge. At high operating speeds, certain airfoils with unique features may deform in a way which may lead to a phenomenon called “closing”. Closing at the leading edges of the blades may cause restricted air flow.